Apparatus for detecting or translating electrical impulses



J. SCOTT-TAGGART APPARATUS FOR DETECTING OR TRANSLATING ELECTRICAL IMPULSES Filed April 3Q, 1921' 6,222? @292 122?" at ga 2" iiirway,

Patented Dec. 27, 1927.

mesa-messes enemas on Tenement E'LncTRIoAn memes;

aiipiicatimi' fiid e iiii a, 1921, Seriai No." 465,731, are mean Britain Ma 20, was:

This invention relates to the detection or translation of electrical impulses, and by translation is meant the production oflocal effects consequent upon the presence or reception of electrical impulses emanating froma'n exter al source, Which effects are notinornially or merely dependent upon the received impulses for their strength or power, although they are in general influenee'd in' their character by the received 1mpulses. I I

In the method involved in the present in vention the frequency of the output signal varies with the intensity of therec'eived impulses'w'hieh pi'oc'liice a change in the interaction of th'e tivo sets' of continuous electrical oscillations, resulting in the production in a suitable indicator of boats or of I change of frecp'ienoy of existing beats. In

the application of the invention to ireless signalling there are produced locally two sets ol continuous electrical oscillations which are arranged to interact on each other so as to produce bea tswli'e'n their frequencies differ. Normally the local circuits are so adjusted and arranged with respect to each other and to a local indicator or detector that no effect is produced on the latter in the absence of electrical impulses emanating from an external source, although alternatively the circuits might be so adjusted as to produce a beat of a definite frequency under such circumstances. In either case, means are provided whereby the reception of external impulses so affects oneor both of the local circuits as to cause a change in their interaction which produces an indica; tion in the detector, e. g. by the production of beats or of a change of frequencyin ex isting beats. V e v In the accompanying drawings Fig. 1 il lustrates one method of carrying the invention into effect and Fig. 2 an arrangement in which a variable resistance in the form of a three-electrode thermionic valve is employed. I propose to use for this purpose a device responsive to changes in frequency of the type described. in British patent specification No. 166,189. Two such deViCes'A and B, comprising three-electrode valves V, V and associated circuits producing continuous oscillations, are so arranged that beats are produced through the interaction of the two sets of oscillations, these beats being rectified by one of the valves and giving audible signals in the telephone receiver T.

If new the frequencies are balaiiced'so that no audible beats'are produced, a' variation of either frequency will upset the balance and give a" note in thetelephones. This change of frequency is effected by the incoming signals'producing a variation of one of the electrical constants or factors of one of-the contii'ifuously oscillating circuits, as for exaniplc a variation of a resistance inserted in one of the'devices A, B across the oscillatory circuit L, C, Which resistance is variedby the incoming signal. v

Fig.- 2 illustrates the use of a'three-electrode valveV as a variable resistance across the grid oscillatory circuit L, C ofan os- Tlatory valve V; The anode circuit of -Jalve coi'itains a retroactor coil, L as commonly used. The valve V is also arranged to produce oscillations of a frequ-ency doterminedby the condenser C and inductance L retroactor coil L and telephones T being included in the anode eircu ts. The filaments of the val'vesobtain their-current from the battery B and the represented by H. The

anode battery is frequency of the oscillations produced by V may be varied by altering the conductivity of the valve V by altering its grid potential. The normal adjustment of this grid potential may be varied by the potentiometor R which thus serves as a means of adjusting accurately thebalance of frequencies. The input potentials are applied to the terminals X, Y.

Such a circuit may be adjusted so that normally nothing is heard in the telephones. Incoming potentials applied to X, Y will upset the, balance of frequencies and give an audible signal in T or other indicator.

If desired, the incomimg signal may be used to alter the frequency-of an existing beat note. i

It will be seen that a strong impulse applied toX, Y will cause such a change in one of the frequencies that the beats are be yond the audible limit. A limiting effect is thus obtainable.

If desired, the apparatus may be adjusted so that normally the beats are beyond the audible limit, but are brought into the audible limit by the input signal.

The apparatus may be used for a very large number of purposes Where it is desired to produce a local output of a frequency dependent on the input strength. It may he used in telegraphy for producing a buzzing carryingthe same into note by the application of direct current potentials. It may be used for the reception of continuous waves, the rectified oscillations being led to the terminals X, Y.

It is desirable in this invention that the frequencies used be of a high order, say 1,000,000, in order that small input potentials may a'trect the balance of frequencies more readily.

heapparatus is especially useful when it is desired to compare the strength of impulses, as in wireless direction finding.

In a further modification the beat currents obtained from the device as hereinbefore described. are arranged to interact with locally produced. alternations of a different frequency so as to produce beats, these secondary beats being used to operate the indicator. With such an arrangement the primary beats may be beyond audible frequency.

Having thus describedthe nature of the said invention and the best means I know of practical effect, I

claim v 1. A method of translating or detecting electrical impulses, wherein the received impulses produce variations in a resistance with consequential change in the interaction of two sets of independently produced continuous electrical oscillations, said change producing in a suitable indicator beats or a change of frequency of existing beats.

2. An apparatus for translating or detecting electricalimpulses,comprising two electrical oscillation generators having'circuits arranged to interact with each other, an indicator associated "therewith and adapted to give indications when the frequencies of the oscillation generatorsdifler, and means responsive to received electrical impulses operating to vary a resistance associated with one i of the oscillating circuits.

3. An, apparatus according to claim 2, wherein the received impulses vary the resistance ofa three-electrode valve shunted across one of the oscillating circuits.

t. An apparatus according to claim 2, wherein the received impulses vary the grid potential and consequently the resistance of a three-electrode valve shunted across one of the oscillating circuits.

5. An apparatus for translating or detecting electrical impulses, comprising a pair of electrical oscillation generators having cir cuits arranged to interact with one another, an indicator associated with said circuits and adapted to show when the frequencies of said generators differ, a three-electrode valve shunted across one of said oseillatingcircuits and of which the grid potential, and consequently the resistance, is varied by the received electrical impulses, and a local potentiometer device for varying the initial grid'potential of said three-electrode valve.

In testimony whereof I have signed my name to this specification.

JOHN SGOTT-TAGGART. 

